Surface light source apparatus

ABSTRACT

A surface light source apparatus has a light emitting element, a light flux controlling member and a light diffusing member. The light flux controlling member has: a light control/emission surface that controls a traveling direction of light; a concavity that allows a main beam to be incident inside; and a back surface that extends in a radial direction from an opening rim part of the concavity and that allows sub-beams to be incident inside. One of a grid convex part which arranges a plurality of strips of convex parts in a grid pattern and a grid concave part which arranges a plurality of strips of concave parts in a grid pattern is formed in the back surface of the light flux controlling member. Surface roughening treatment is applied to one of the strips of the convex parts and the strips of the concave parts.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/911,562, filed on Jun. 6, 2013, which is a continuation of U.S.patent application Ser. No. 13/483,188, filed on May 30, 2012, now U.S.Pat. No. 8,487,526; which is a continuation of U.S. patent applicationSer. No. 12/768,108, filed on Apr. 27, 2010, now U.S. Pat. No.8,227,969; which claims the benefit of Japanese Patent Application No.2009-107848, filed on Apr. 27, 2009, Japanese Patent Application No.2009-222574, filed on Sep. 28, 2009, and Japanese Patent Application No.2010-85182, filed on Apr. 1, 2010, the disclosures of which, includingthe specifications, drawings and abstracts, are incorporated herein byreference in their entirety.

TECHNICAL FIELD

The present invention relates to a light emitting apparatus, surfacelight source apparatus and display apparatus. For example, the presentinvention relates to: a light emitting apparatus used for variousilluminations such as light sources of a backlight planarly illuminatinga liquid crystal display panel from the back or general illumination ina room; a surface light source apparatus used for various illuminations;and a display apparatus using the surface light source apparatus as anilluminating means in combination with a member-to-be-illuminated.

BACKGROUND OF THE INVENTION

Conventionally, a surface light apparatus that uses a plurality of lightemitting diodes (“LEDs”) as point light sources is known as anilluminating means for a liquid crystal monitor used in a personalcomputer, television and so on.

The surface light source apparatus arranges a plurality of LEDs in amatrix shape on the back surface of a flat light flux controlling memberhaving virtually the same shape as a liquid crystal panel of a liquidcrystal display monitor. The surface light source apparatus allows lightemitted from the LEDs to be incident inside the light flux controllingmember, and controls the traveling direction of light when emittinglight from the light flux controlling member. Then, the surface lightsource apparatus diffuses light emitted from the light flux controllingmember by a light diffusing member, and then planarly illuminates theliquid crystal display panel from the back.

Patent Literature 1 discloses a planar light source from which lighthaving transmitted through an optical element is emitted virtuallyvertically with respect to the plane surface. FIG. 1 schematically showsa surface light source apparatus that uses as light sources the LEDsdisclosed in Patent Literature 1. As shown in FIG. 1, in surface lightsource apparatus 100, micro lens arrays 102 are arranged to meet aplurality of LEDs 101 on a one-by-one basis. Micro lens arrays 102control the traveling directions of light emitted from LEDs 101, so thatsurface light source apparatus 100 emits light in the direction verticalto the plane surface of the substrate (i.e. upward).

Patent Literature 2 discloses a display apparatus in which a hollow partis formed inside a convex part of a lens case and in which void partswith inclining surfaces which reflect light emitted in the horizontaldirection from a light emitting element, toward the convex parts, areformed outside the outer periphery of the hollow part.

FIG. 2 is a configuration diagram showing a display apparatus disclosedin Patent Literature 2. As shown in FIG. 2, matrix display apparatus 130aligns light emitting elements 132 in a matrix shape, on display panelsubstrate 131, and arranges lens cases 133 on the side of the surface oflight emitting elements 132. Lens case 133 is mounted on display panelsubstrate 131 to be closely attached. In lens case 133, convex part 134of virtually a semispherical shape is formed in the position meetinglight emitting element 132, and hollow part 135 that includes lightemitting element 132 inside convex part 134 is formed. The sidewalls ofhollow part 135 takes in light emitted from light emitting element 132by refracting the light such that the light travels toward the frontside (i.e. upward in FIG. 2). The sidewalls of hollow part 135 are onlythe incidence planes for light emitted from light emitting element 132.Further, in lens case 133, void parts 136 are formed around hollow part135 that includes light emitting element 132. Void parts 136 totallyreflect light emitted in the horizontal direction from light emittingelement 132 and taken in by lens case 133, toward the front side throughinclining surfaces 137 of void parts 136 and insulating substrate 138.By this means, the luminance of illumination light in the front side ofmatrix display apparatus 130 increases.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent Application Laid-Open No.    2002-49326-   Patent Literature 2: Japanese Patent Application Laid-Open No.    2001-250986

SUMMARY OF INVENTION Technical Problem

However, with this conventional surface light source apparatus, lightemitted from a light emitting element is incident on the back surface ofa light flux controlling member (i.e. the surface facing the substrate)and the light flux controlling member concentrates and emits this light,and therefore there is a problem that unevenness in illuminance isproduced on the illuminated surface. The unevenness in illuminanceprevents uniform planar illumination, and deteriorates quality ofillumination.

It is therefore an object of the present invention to provide a lightemitting apparatus, surface light source apparatus and display apparatusthat can prevent unevenness in illuminance.

Solution to Problem

The surface light source apparatus according to the present inventionemploys a configuration which includes: a light emitting element thatemits light; a light flux controlling member that controls light emittedfrom a light emitting element; and a light diffusing member thatscatters light and allows transmission of light emitted from the lightemitting apparatus, in which the light flux controlling membercomprises: a light control/emission surface that controls a travelingdirection of the light emitted from the light emitting element; aconcavity that allows a main beam to be incident inside, the main beambeing light emitted in a predetermined range of an angle from areference optical axis serving as a center axis of three-dimensionallight fluxes emitted from the light emitting element; and a back surfacethat extends in a radial direction from an opening rim part of theconcavity and that allows sub-beams to be incident inside, the sub-beamsbeing light other than the main beam emitted from the light emittingelement, in which one of a grid convex part which arranges a pluralityof strips of convex parts in a grid pattern and a grid concave partwhich arranges a plurality of strips of concave parts in a grid pattern,is formed in the back surface of the light flux controlling member, andin which surface roughening treatment is applied to one of the strips ofthe convex parts and the strips of the concave parts.

Advantageous Effects of Invention

The present invention can scatter light incident on the back surface ofa light flux controlling member, out of light emitted from lightemitting elements. As a result, it is possible to provide uniformilluminance on the illuminated surface on which light is radiated fromthe light flux controlling member, and provide high quality ofillumination.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 schematically shows a conventional surface light source apparatusthat uses LEDs as light sources;

FIG. 2 is a configuration diagram showing a conventional displayapparatus;

FIG. 3 illustrates the basic principle of the present invention;

FIG. 4 is a plan view of a surface light source apparatus forming adisplay apparatus according to Embodiment 1 of the present invention;

FIG. 5 is a cross-sectional view of a display apparatus cut along lineX1-X1 in FIG. 4;

FIG. 6 shows a detailed configuration of a light flux controlling memberof a surface light source apparatus according to Embodiment 1 of thepresent invention;

FIGS. 7A and 7B show a detailed configuration of a light fluxcontrolling member of a surface light source apparatus according toEmbodiment 1 of the present invention;

FIG. 8 shows a detailed configuration of a light flux controlling memberof a surface light source apparatus according to Embodiment 1 of thepresent invention;

FIG. 9 is a perspective view schematically showing the structure of agrid convex part by cutting part of the back surface of a light fluxcontrolling member of a surface light source apparatus according toEmbodiment 1 of the present invention;

FIG. 10 illustrates the operation of a light flux controlling memberforming a grid convex part in the back surface of a light fluxcontrolling member of a surface light source apparatus according toEmbodiment 1 of the present invention;

FIG. 11 illustrates the operation of a light flux controlling memberforming a smooth surface as the back surface of a light flux controllingmember of a surface light source apparatus according to Embodiment 1 ofthe present invention;

FIGS. 12A and 12B show the distribution of illuminance of light on anilluminated surface of a light flux controlling member of a surfacelight source apparatus according to Embodiment 1 of the presentinvention;

FIGS. 13A, 13B and 13C illustrate convex parts formed in the backsurface of a light flux controlling member of a surface light sourceapparatus according to Embodiment 1 of the present invention;

FIGS. 14A and 14B illustrate scattered light and convex parts formed inthe back surface of a light flux controlling member of a surface lightsource apparatus according to Embodiment 1 of the present invention;

FIGS. 15A and 15B illustrate scattered light and convex parts formed inthe back surface of a light flux controlling member of a surface lightsource apparatus according to Embodiment 1 of the present invention;

FIGS. 16A and 16B illustrate scattered light and convex parts formed inthe back surface of a light flux controlling member of a surface lightsource apparatus according to Embodiment 1 of the present invention;

FIGS. 17A and 17B are cross-sectional views of a light flux controllingmember of a light emitting apparatus according to Embodiment 2 of thepresent invention;

FIG. 18 is a perspective view schematically showing the structure of agrid convex part by cutting part of the back surface of a light emittingapparatus according to Embodiment 2 of the present invention;

FIGS. 19A and 19B are cross-sectional views of a light flux controllingmember of a light emitting apparatus according to Embodiment 3 of thepresent invention;

FIGS. 20A and 20B illustrate how light is retroreflected on the backsurface of a light flux controlling member of a light emitting apparatusaccording to Embodiment 3 of the present invention;

FIGS. 21A and 21B illustrate how light is retroreflected on the backsurface of a light flux controlling member of a light emitting apparatusaccording to Embodiment 3 of the present invention;

FIG. 22 shows the result of simulation to verify advantages of a lightemitting apparatus according to Embodiment 3 of the present invention;

FIG. 23 shows variation of a light flux controlling member of a lightemitting apparatus according to Embodiment 3 of the present invention;

FIGS. 24A and 24B are cross-sectional views of a light flux controllingmember of a light emitting apparatus according to Embodiment 4 of thepresent invention;

FIGS. 25A, 25B and 25C schematically show the structure of the gridconcave-convex parts by cutting part of the back surface of the lightflux controlling member of variation 1 of a light emitting apparatusaccording to Embodiment 5 of the present invention;

FIGS. 26A, 26B and 26C schematically show the structure of the gridconcave part by cutting part of the back surface of the light fluxcontrolling member of variation 2 of a light emitting apparatusaccording to Embodiment 5 of the present invention; and

FIG. 27 schematically shows the structure of the grid concave-convexpart by cutting part of the back surface of the light flux controllingmember of variation 3 of a light emitting apparatus according toEmbodiment 5 of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be explained indetail with reference to the accompanying drawings.

(Explanation of Principle)

The basic concept of the present invention will be explained.

FIG. 3 illustrates the basic principle of the present invention.

Conventionally, light incident from the back surface of a light fluxcontrolling member was not taken into account. The present inventorshave found based on experiments that, if such light is incident inside alight flux controlling member from the back surface of the light fluxcontrolling member, the light flux controlling member concentrates andemits this light, thereby producing unevenness in illuminance on theilluminated surface. Further, it has been found that it is not possibleto prevent unevenness in illuminance from being produced by simplyroughening the back surface of the light flux controlling member.

Then, the present inventors have found a configuration to form a gridpattern of a plurality of convex parts or a plurality of concave partsin the back surface of the light flux controlling member, in order toscatter light incident from light emitting elements on the back surfaceof the light flux controlling member. This configuration has thefollowing characteristics.

FIG. 3 is a coordinate axis which serves as a guide to arrange the lightflux controlling member. A light emitting point, which is one spot onthe emission plane of a light emitting element, is arranged in origin Oin the XYZ orthogonal coordinates, and the back surface of the lightflux controlling member is arranged on plane S which is distant apartfrom origin O and parallel to the X-Y plane, such that the referenceoptical axis of the light flux controlling member matches the Z axis. Incase where the intersection point between the reference optical axis ofthe light flux controlling member and plane S is point P0, points ofincidence of light emitted from origin O are “point P1” on theintersection line between above plane S and a pyramidal plane of avirtual circular cone having origin O as the vertex, and “point P2”rotating point P1 by θ1=45 degrees around the Z axis as the rotationaxis. For example, by forming a grid pattern of a plurality of strips ofconvex parts (i.e. protrusions) or strips of concave parts (i.e.grooves) in the back surface of the light flux controlling member, suchthat ridge lines extend in the direction orthogonal to line P0-P1, it ispossible to allow anisotropic refraction of light emitted from origin O.Further, distance L1 between the reference optical axis and a point onilluminated plane S′ which light incident on point P1 reaches and whichis parallel to plane S differs from distance L2 between the referenceoptical axis and a point on illuminated plane S′ which light incident onpoint P2 reaches. By this means, it is possible to prevent an annular,discriminating bright part from being produced on an illuminatedsurface.

Embodiment 1 Overall Shape of Surface Light Source Apparatus

FIG. 4 is a plan view of a surface light source apparatus forming adisplay apparatus according to Embodiment 1 based on the above basicconcept. Note that FIG. 4 does not show a member-to-be-illuminated suchas a liquid crystal display panel. FIG. 5 is a cross-sectional viewcutting the display apparatus of FIG. 4 along line X1-X1. The presentembodiment provides an example where the surface light source apparatusis applied to a liquid crystal panel.

As shown in FIG. 4, surface light source apparatus 1 has flat lightdiffusing member 2, light emitting elements 3 of light sources and lightflux controlling members 4. Light diffusing member 2 is arranged on theback surface of a member-to-be-illuminated such as a liquid crystaldisplay panel, and has virtually the same shape as themember-to-be-illuminated. A plurality of light emitting elements 3 arearranged at virtually equal intervals of pitch P, on the back surface oflight diffusing member 2. Light flux controlling members 4 control thetraveling directions of light fluxes emitted from light emittingelements 3.

Above light emitting element 3 and light flux controlling member 4 formlight emitting apparatus 5.

As shown in FIG. 5, display apparatus 6 is formed with surface lightsource apparatus 1 and member-to-be-illuminated 7 that is arranged onthe side of emission plane 8 (i.e. plane on the opposite side of backsurface 9) of light diffusing member 2.

Light diffusing member 2 is formed to have a shape of a sheet or a flatshape by resin material of good optical transparency such as PMMA(PolyMethylMethAcrylate) and PC (PolyCarbonate). Light diffusing member2 is formed in virtually the same size as the flat shape of amember-to-be-illuminated such as a liquid crystal display panel,advertisement display panel and signpost display panel.

In the surface of light diffusing member 2, minute irregularities (i.e.prism-shaped protrusions or irregularities formed by embossing treatmentor diffusion processing such as bead coating) are formed, or a diffusingmaterial is mixed inside light diffusing member 2.

By means of this treatment, light diffusing member 2 diffuses lightwhile allowing transmission of light emitted from light controllingemission surface 11 (see FIG. 6) of light flux controlling member 4, andmakes light radiated on the member-to-be-illuminated uniform.

Light emitting elements 3 are, for example, LEDs. Light emittingelements 3 are arranged in a matrix shape, on the back surface of lightdiffusing member 2.

Light flux controlling member 4 is an expanding lens that controls thetraveling directions of light emitted from light emitting elements 3,and is, for example, an aspheric lens. Light flux controlling member 4is made of transparent resin material such as PMMA(PolyMethylMethAcrylate), PC (Polycarbonate) and EP (EPoxy resin) ortransparent glass.

[Overall Shape of Light Flux Controlling Member 4]

FIG. 6 to FIG. 8 show the detailed configuration of above light fluxcontrolling member 4. FIG. 6 is a plan view of light flux controllingmember 4, FIG. 7A is a cross-sectional view showing FIG. 6 from lineA-A′ indicated by arrows, FIG. 7B is a view enlarging part C shown inFIG. 7A, and FIG. 8 is a bottom view of above light flux controllingmember 4.

FIGS. 7A and 7B illustrates the shape of light flux controlling member 4including reference optical axis L of light emitting element 3.Reference optical axis L refers to the traveling direction of light thatis a virtual beam representing light fluxes, and that is in the centerof three-dimensional light fluxes emitted from light emitting element 3.A case will be explained with the present embodiment where the opticalaxis of light emitting element 3 (i.e. the optical, center axis of lightemitting element 3) matches reference optical axis L.

As shown in FIG. 6 to FIG. 8, light flux controlling member 4 has lightcontrolling emission surface 11, back surface 12 and concavity 14. Lightcontrolling emission surface 11 controls the emission direction to emitlight which is emitted from light emitting element 3 and which isincident inside light flux controlling member 4. Concavity 14 allows amain beam, which is light emitted at a predetermined range of angles inthe reference optical axis direction out of light emitted from lightemitting element 3, to be incident inside. Back surface 12 extends fromthe opening rim part of concavity 14 in the radial direction, and allowssub-beams, which are light other than the above main beam and which areemitted from light emitting element 3 at a wide angle with respect tothe reference optical axis, to be incident inside. In back surface 12,grid convex part 13 that scatters light incident on back surface 12 oflight flux controlling member 4 from light emitting element 3 is formed.

Further, light flux controlling member 4 has: flange 15 of virtually anannular shape that projects outward in the radial direction of lightcontrolling emission surface 11; legs 16 of a round stick shape thatattach light flux controlling member 4 to substrate 18 (see FIG. 5) in astate where light flux controlling member 4 is positioned in substrate18; and protrusions 17 that guide the positioning of legs 16.

Light controlling emission surface 11 projects upward above flange 15(to the side of light diffusing member 2) as shown in FIG. 7A.

Three legs 16 are formed at equal intervals on the circumference of theconcentric circle of the inner peripheral surface of flange 15.Protrusions 17 meet the positions of three legs 16, and are formed toproject outward in the radial direction of flange 15.

Legs 16 are adhered to surface 18 a (see FIG. 5) of substrate 18 in astate where light flux controlling member 4 is positioned with respectto substrate 18, so that light flux controlling member 4 is attached tosubstrate 18.

When light flux controlling member 4 is attached to substrate 18, gap εis formed between the light emission surface of light emitting element 3and back surface 12 (i.e. reference plane) of light flux controllingmember 4 (see FIG. 5). There are reasons for forming gap ε, including apassive reason that there is error of attachment when light fluxcontrolling member 4 is mounted on substrate 18 to accommodate lightemitting element 3 in concavity 14, and the positive reason that thereis a purpose of releasing heat discharged from light emitting element 3.

[Light Control/Emission Surface 11 of Light Flux Controlling Member 4]

Light control/emission surface 11 of light flux controlling member 4 isformed with: first emission surface 11 a that is positioned in apredetermined range around optical axis L; second emission surface 11 bthat is formed to continue to the periphery of first emission surface 11a; and third emission surface 11 c that connects second emission surface11 b with flange 15.

As shown in FIG. 7A, first emission surface 11 a has a shape of a smoothcurved surface dented downward, and is shaped like a partially removedsphere providing a concave configuration. Further, second emissionsurface 11 b is formed to continue to first emission surface 11 a, has asmooth curved shape bulging upward and, when seen from a plan view, isformed in a shape of virtually a hollow disk surrounding first emissionsurface 11 a. Furthermore, third emission surface 11 c is formed tocontinue to second emission surface 11 b, and the cross section thereofis formed as virtually a straight inclining surface. Still further,third emission surface 11 c may be formed in a curved shape as long asthe curved shape does not prevent uniform emission in a wide range fromlight flux controlling member 4.

[Grid Convex Part 13 of Light Flux Controlling Member 4]

As described above, light flux controlling member 4 is supported onsubstrate 18 by legs 16, gap c is formed between back surface 12 oflight flux controlling member 4 and the light emission surface of lightemitting element 3 to radiate heat. This gap c is formed, so that partof light emitted from the light emission surface of light emittingelement 3 is incident inside light flux controlling member 4 from backsurface 12 of light flux controlling member 4. If back surface 12 is asmooth surface, light reaching back surface 12 of light flux controllingmember 4, that is, the lens bottom surface, is refracted closer toreference optical axis L, is incident inside light flux controllingmember 4, and is emitted from light control/emission surface 11. Thisemitting light is not light that cannot be controlled by light fluxcontrolling member 4 to smoothly widen and emit, and that naturallyconcentrates through smooth back surface 12 and light control/emissionplane 12 and produces an annular bright part on the illuminated surface,thereby producing unevenness in illuminance (described later using FIG.12B).

With the present embodiment, grid convex part 13 is formed in backsurface 12 of light flux controlling member 4 to scatter light which isincident on back surface 12 of light flux controlling member 4. That is,between the beam which is incident from arbitrary light incident pointP1 on back surface 12 and the beam which is incident from light incidentpoint P2 that is determined by rotating this light incident point P1 45degrees around reference optical axis L as the axis of rotation, theangle in each light incident point with respect to the normal line ofback surface 12 varies. Accordingly, illuminated part (i.e. thetrajectory which light reaching the illuminated surface draws on theilluminated surface) acquired by light incident from each point on thetrajectory determined by rotating light incident point P1 360 degreesaround reference optical axis L as the axis of rotation, does not becomeannular, and is scattered in a wide range.

The shape of each strip of grid convex part 13 only needs tosufficiently scatter light incident on back surface 12 of light fluxcontrolling member 4, the cross-sectional shape orthogonal to thedirection in which the protrusions extend may have a triangular shape, atriangular shape having its vertex subjected to R-chamfer processing, ora semi-circular shape, and, moreover, groove parts between these stripsmay have round shapes. Further, although, if the transferability fortransferring light flux controlling member 4 from the mold is taken intoaccount, each protruding part of grid convex part 13 preferably has acurved shape, a triangular cross-sectional shape is desirable for thepurpose of preventing refraction of light in the optical axis direction.Furthermore, the present inventors have found based on experiments thatit is preferable to arrange convex parts in a grid pattern tosufficiently scatter light incident on back surface 12 of light fluxcontrolling member 4.

As shown in FIG. 7A and FIG. 8, grid convex part 13 is formed in backsurface 12 of light flux controlling member 4. Characteristics of gridconvex part 13 include that (1) grid convex part 13 has convex parts and(2) is formed in a grid pattern.

(1) Convex Part

As shown in FIG. 7B, grid convex part 13 is formed by aligning aplurality of strips of convex parts 13 a projecting outward from backsurface 12 of light flux controlling member 4 such that the ridge linesof these convex parts 13 a become parallel, and by aligning a pluralityof strips of convex parts 13 b (see FIG. 9 described later) orthogonalto those convex parts 13 a such that the ridge lines of these convexparts 13 b become parallel. The cross-sectional shape of convex part 13a orthogonal to the direction in which a strip extends has a similarshape to a semi-circle, and has a triangular shape having its apexsubjected to R-chamfer processing. For example, the length of the bottomsurface of convex part 13 a is 0.5 millimeters, the base angle of theinclining surface forming a strip is 45 degrees and R at the tip is 0.2millimeters. Although the inclining angle of convex part 13 a may besmaller than 45 degrees, the inclining angle of convex part 13 a ispreferably 45 degrees or greater for the purpose of scattering lightincident on back surface 12 of light flux controlling member 4.

Grid convex part 13 is transferred from the mold using transparent resinmaterial such as PMMA, PC and EP, to back surface 12 of light fluxcontrolling member 4, and is formed integrally with the main body oflight flux controlling member 4. Therefore, if the inclining angle ofconvex part 13 a is great, there is a possibility that it is necessaryto facilitate transferring by applying high temperature to resin or amold or by applying dwelling sufficiently to prevent a sink mark inorder to achieve accurate transferring required upon molding, andtherefore time is required for cooling or dwelling and cost increases.

With the present embodiment, by making the cross-sectional shape ofconvex part 13 a virtually a semi-circular shape, grid convex part 13can sufficiently scatter light incident on back surface 12 of light fluxcontrolling member 4, and facilitate transferring from the mold uponmolding of light flux controlling member 4 to reduce the manufacturingcost.

(2) Grid Pattern

As shown in FIG. 8, grid convex part 13 is formed with the aboveplurality of convex parts 13 a and convex parts 13 b orthogonal to theseconvex parts 13 a (see FIG. 9 described later). Here, grid convex part13 only needs to be provided in a predetermined area from the center ofback surface 12 of light flux controlling member 4 to the outerperiphery. In FIG. 8, grid convex part 13 is formed almost up to theinner periphery of legs 16. Grid convex part 13 may be formed in theentire surface of back surface 12 of light flux controlling member 4.

FIG. 9 is a perspective view schematically showing a structure bycutting part of grid convex part 13.

As shown in FIG. 9, grid convex part 13 is formed by making a pluralityof convex parts 13 a and a plurality of convex parts 13 b havingvirtually a semicircular cross-sectional shape orthogonal to each otherin a grid pattern. In case where convex parts are formed in a gridpattern and thereby a circular cone symmetrical to reference opticalaxis L which assumes one point on the light emission surface of lightemitting element 3 as the vertex is virtually arranged, such that thebottom surface of this circular cone overlaps back surface 12 of lightflux controlling member 4, the shape formed by connecting intersectionpoints between back surface 12 and beams that are emitted from thevertex of the circular cone and that travel along the pyramidal plane,matches the shape of the periphery (i.e. circular shape) of the bottomsurface of the circular cone. However, the shape formed on theilluminated surface of member-to-be-illuminated 7 by the intersectionpoints between member-to-be-illuminated 7 and beams emitted from lightflux controlling member 4 after having passed the above intersectionpoints does not become circular. Accordingly, it is possible to scatterlight incident on back surface 12 of light flux controlling member 4, ineither the vertical direction or the horizontal direction. By contrastwith this, if the above convex parts are provided in a radial patternfrom the center rather than in a grid pattern, or protrusions of acircular conical shape are formed at uniform pitches, there are caseswhere a strong concentrated light pattern having regularity is producedon the illuminated surface, and there are possibilities that lightconcentrates in a narrow range on the illuminated surface, therebyproducing a discriminating bright part.

Further, when the convex parts are formed in a grid pattern, theilluminance value of the bright part is low compared to the case whereback surface 12 is smooth. As described above, by forming convex partsin a grid pattern, it is possible to readily process a mold required totransfer a shape for scattering light sufficiently, by means ofinjection molding and, consequently, reduce manufacturing cost.

[Operation of Light Flux Controlling Member 4]

Hereinafter, the operation of light flux controlling member 4 configuredas described above will be explained.

FIG. 10 illustrates the operation of light flux controlling member 4forming grid convex part 13 in back surface 12 of light flux controllingmember 4. FIG. 11 illustrates the operation of light flux controllingmember 4 forming back surface 12 of light flux controlling member 4 as asmooth surface (that is, a smooth surface in which grid convex part 13is not formed). FIGS. 12A and 12B shows the distribution of illuminanceof light on a surface illuminated by light emitted from light fluxcontrolling member 4, that is, the distribution of illuminance on theback surface (i.e. illuminated surface) of light diffusing member 2. Asa comparison example of Embodiment 1, FIG. 12A shows the distribution ofilluminance of light on the surface illuminated by light radiated fromlight flux controlling member 4 in which grid convex part 13 of FIG. 10is formed, and FIG. 12B shows the distribution of illuminance of lighton the surface illuminated by light radiated from light flux controllingmember 4 forming back surface 12 of FIG. 11 as a smooth surface. Thevertical axis and horizontal axis each represent the dimensions fromreference optical axis L of light emitting apparatus 5.

First, as shown in FIG. 10 and FIG. 11, most of light in the rangecovering a half-intensity-angular-range of light emitted from lightemitting element 3 is incident on light flux controlling member 4 fromconcavity 14, transmits inside light flux controlling member 4 and thenis outputted to the outside (i.e. in the air) from first emissionsurface 11 a to third emission surface 11 c according to Snell's law. Atthis time, light fluxes emitted from light flux controlling member 4smoothly spread in the range of illumination.

However, gap c is formed between substrate 18 (see FIG. 5) and backsurface 12 of light flux controlling member 4, and therefore lightenters this gap c from the light emission surface of light emittingelement 3 and is incident inside light flux controlling member 4 fromback surface 12 of light flux controlling member 4.

As shown in FIG. 11, if back surface 12 of light flux controlling member4 is a smooth surface, that is, if grid convex part 13 is not formed inlight flux controlling member 4, light incident on back surface 12 (i.e.lens bottom surface) of light flux controlling member 4 travels insidelight flux controlling member 4 in a state where light is refractedcloser to the reference optical axis L, and is emitted from secondemission surface 11 b and third emission surface 11 c. As a result,refraction in the incidence plane to light flux controlling member 4 andconcentration of light by the emission plane of a convex lens shape oflight flux controlling member 4 produce annular unevenness inilluminance 21 on the illuminated surface in which the part (i.e.luminous part) where light is concentrated is lighted up annularly andmore brightly than other parts. Annular unevenness in illuminance 21 isseen from the side of the emission plane of light diffusing member 2,and deteriorates quality of illumination.

By contrast with this, with the present embodiment, light incident onback surface 12 of light flux controlling member 4 is scattered byforming grid convex part 13 in back surface 12 of light flux controllingmember 4.

As shown in FIG. 10, if grid convex part 13 is formed in back surface 12of light flux controlling member 4, in order to scatter light by gridconvex part 13, light incident on back surface 12 (i.e. lens bottomsurface) of light flux controlling member 4 is emitted from light fluxcontrolling member 4 in a wide range of the illuminated surface withoutbeing concentrated closer to reference light axis L. As a result, asshown in FIG. 12A, unevenness in illuminance 22 on the illuminatedsurface is reduced significantly. Although, in FIG. 12A, the phrase“unevenness in illuminance 22” is used for ease of explanation, thedifference in light intensity is actually small and needs not to bereferred to as “unevenness in illuminance 22” given the level of thedifference. Further, for unevenness in illuminance 22, not only thedifference in light intensity is suppressed substantially littlecompared to annular unevenness in illuminance 21 of FIG. 12B, but alsobright parts are discrete as shown in FIG. 12A, so that parts (i.e.bright parts) where light gathers is distributed in a state whereunevenness in illuminance is less distinct. Unevenness in illuminance 22of FIG. 12A shows a discrete cross shape because grid convex part 13 hasa square grid.

By the way, if the optical path of light incident from back surface 12of light flux controlling member 4 can be scattered, it is possible toprovide the same advantage as the present embodiment. However, thepresent inventors have found based on experiments that a mere diffusingsurface cannot provide a sufficient advantage.

As a general method of diffusing light, forming a rough surface in backsurface 12 of light flux controlling member 4 is possible. A roughsurface can readily be created by applying etching processing to thesurface which becomes a mold of light flux controlling member 4 androughening the surface.

FIGS. 13A, 13B and 13C illustrates convex parts formed in back surface12 of light flux controlling member 4. FIG. 13A shows convex parts ofgrid convex part 13. Further, FIG. 13B shows back surface 12 to whichsurface roughening processing is applied. Furthermore, FIG. 13C showsthe surface of the mold which is roughened to form a rough surface inback surface 12, and back surface 12 to which the shape of the roughenedsurface is transferred.

As shown in FIG. 13C, with surface roughening processing using a popularetchant, transfer surface 31 formed in the mold is very fine (i.e. inunits on the order of micrometers). By applying such fine treatmentprocessing to back surface 12 of light flux controlling member 4, it isnot possible to sufficiently scatter incident light. However, furtheradding these fine irregularities to grid convex part 13 of the presentembodiment shows an effect of further diffusing light. This will bedescribed later in Embodiment 2.

In case where light flux controlling member 4 is transferred fromtransfer surface 32 of the mold and formed by injection molding and soon, if the temperature setting or dwelling applied to the resin and moldare not appropriate, back surface 12 of light flux controlling member 4provides irregular treated surface 31 much smoother than fineirregularities on transfer surface 32 of the mold and therefore itbecomes impossible to scatter incident light sufficiently. Performingmore accurate transferring from transfer surface 32 of the mold makesthe molding cycle longer and requires substantial time and adjustment,thereby increasing cost.

If height d of rough surface 33 of FIG. 13B is made as high as convexpart 13 a of grid convex part 13 of FIG. 13A by performing surfaceroughening processing using a special etchant or file, it is possible toscatter incident light. However, the present inventors have found thatthis surface roughening processing has the following drawback inaddition to the increase in cost. That is, while the surface rougheningprocessing applied to back surface 12 of light flux controlling member 4needs to provide a sufficient amount of difference in height d in oneconvex part of rough surface 33, transferring becomes insufficient ifthe molding cycle of rough surface 33 shown in FIG. 13B is made a littleshorter, and therefore it is not possible to provide the required amountof difference in height d. For the same reason as in the case where backsurface 12 of light flux controlling member 4 is a smooth surface, inrough surface 33 that does not provide such sufficient difference inheight d, light radiated from the light emission surface of lightemitting element 3 is refracted closer to reference optical axis L onback surface 12 (i.e. lens bottom surface) of light flux controllingmember 4. Accordingly, after this light is emitted from light fluxcontrolling member 4 and is concentrated on the illuminated surface,thereby producing unevenness in illuminance.

As described above, general surface roughening processing cannotsufficiently scatter optical paths of light incident from back surface12 of light flux controlling member 4. Even though surface rougheningprocessing for general use can form convex parts, optically speaking,this surface roughening processing produces the same unevenness inilluminance as in the case where back surface 12 is a smooth surface.

Therefore, with the present embodiment, as shown in FIG. 13A, instead ofsurface roughening treatment for forming a processed surface with alittle difference in height using an etchant or file, grid convex part13 is accurately formed in back surface 12 of light flux controllingmember 4.

[Explanation of Convex Parts and Scattered Light]

FIG. 14A to FIG. 16B illustrate convex parts 13 a formed in back surface12 of light flux controlling member 4 and scattered light of lightincident on the convex parts. FIG. 14A shows the direction of beam seenfrom the side of back surface 12 where a beam is incident on backsurface 12 in case where convex parts 13 a are formed in back surface 12of light flux controlling member 4 such that convex parts 13 a areparallel to the X axis of the XYZ orthogonal coordinates. Further, FIG.14B schematically shows the shape in FIG. 14A seen from the lateral side(i.e. from the X axis direction). FIG. 15A shows the direction of beamincident from the orthogonal direction on convex parts 13 a of backsurface 12 of light flux controlling member 4 shown in FIG. 14A.Further, FIG. 15B shows that the operation of convex parts 13 a of backsurface 12 of light flux controlling member 4 works on beams incidentfrom the orthogonal direction. FIG. 16A shows the direction of beamincident from the oblique direction of 45 degrees on convex parts 13 aof back surface 12 of light flux controlling member 4. Further, FIG. 16Bshows that the operation of convex parts 13 a of back surface 12 oflight flux controlling member 4 works on beams incident from the obliquedirection of 45 degrees. One of beams shown in FIG. 15B matches the beamindicated by line 0-P1 in above FIG. 3, and one of beams shown in FIG.16B matches the beam indicated by line O-P2 in above FIG. 3.

As shown in FIG. 14B, convex parts 13 a are formed in back surface 12 oflight flux controlling member 4. As shown in FIG. 14A, the direction ofbeam x parallel to convex parts 13 a and the direction of beamorthogonal to convex parts 13 a are assumed.

When light is incident from the direction orthogonal to convex parts 13a of back surface 12 of light flux controlling member 4 as shown in FIG.15A, the incident angles of light incident on convex parts 13 a vary asshown in FIG. 15B. Therefore, light incident on back surface 12 (i.e.the lens bottom surface) of light flux controlling member 4 is notconcentrated and is emitted from light control/emission surface 11 oflight flux controlling member 4 as scattered light.

Similarly, when light is incident from the oblique direction of 45degrees on convex parts 13 a of back surface 12 of light fluxcontrolling member 4 as shown in FIG. 16A, incident angles of lightincident on convex parts 13 a vary as shown in FIG. 16B. Further, lightis incident on convex parts 13 a at an angle (at 45 degrees in thiscase), and therefore the incident angles of light in the heightdirection and the depth direction of FIG. 16B also vary. Therefore,light incident on back surface 12 (i.e. lens bottom surface) of lightflux controlling member 4 is emitted from light control/emission surface11 of light flux controlling member 4 as scattered light without beingconcentrated.

As explained above in detail, with the present embodiment, grid convexpart 13 that is formed with a plurality of strips and that scatter lightincident on the back surface of light flux controlling member 4 fromlight emitting element 3, is formed in back surface 12 of light fluxcontrolling member 4. By this means, light incident on back surface 12(i.e. lens bottom surface) of light flux controlling member 4 isscattered without being concentrated, and is emitted from lightcontrol/emission surface 11 in a wide range on the illuminated surface.As a result, as shown in FIG. 12A, it is possible to realize uniformilluminance by preventing unevenness in illuminance on the illuminatedsurface, and provide high quality of illumination.

Further, with the present embodiment, in case where gap is formedbetween the light emission surface of light emitting element 3 and backsurface 12 of light flux controlling member 4 when light fluxcontrolling member 4 is attached to substrate 18, light incident on backsurface 12 (i.e. lens bottom surface) of light flux controlling member 4is prevented from being concentrated closer to reference optical axis L.As described above, with the present embodiment, gap c is allowedbetween the light emission surface of light emitting element 3 and backsurface 12 of light flux controlling member 4, so that the excessiveaccuracy of attachment is not required. Consequently, with the presentembodiment, cost is reduced because light emitting element 3 of generaluse can be used instead of an expensive light emitting elementminiaturized to a size that can be accommodated inside concavity 14.

For the same reason, with the present embodiment, in case where theentire area of back surface 12 of light flux controlling member 4becomes an incidence plane, it is possible to provide high quality ofillumination. Further, with the present embodiment, it is possible toprovide a quality illuminated surface even if a light flux controllingmember is arranged in a position the predetermined dimension apart froma light emitting element, and suppress negative influences caused byheat discharged by the light emitting element.

Embodiment 2 Overall Shape of Light Flux Controlling Member

FIGS. 17A and 17B is a cross-sectional view of a light flux controllingmember of a light emitting apparatus according to Embodiment 2. FIG. 17Ais a cross-sectional view of a light flux controlling member, and FIG.17B is a view enlarging part C shown in FIG. 17A. In FIGS. 17A and 17B,the same components as in FIGS. 7A and 7B will be assigned the samereference numerals, and explanation thereof will be omitted.

Light flux controlling member 40 is used instead of light fluxcontrolling member 4 of FIG. 4 and FIG. 11.

In comparison of light flux controlling member 40 shown in FIG. 17A withlight flux controlling member 4 shown in FIG. 7A, the shape of gridconvex part 43 differs from the shape of grid convex part 13.

Grid convex part 43 is transferred from the mold using transparent resinmaterial such as PMMA, PC and EP, to back surface 12 of light fluxcontrolling member 40, and is formed integrally with light fluxcontrolling member 40.

As shown in FIG. 17B and FIG. 18, grid convex part 43 is formed byaligning a plurality of strips of convex parts 43 a projecting outwardfrom back surface 12 of light flux controlling member 40, such that theridge lines of these convex parts 43 a become parallel, and by aligninga plurality of strips of convex parts 43 b orthogonal to those convexparts 43 a, such that the ridge lines of these convex parts 43 b becomeparallel. Then, concave parts are formed between convex parts 43 a andconvex parts 43 a that are adjacent and between convex parts 43 b andconvex parts 43 b that are adjacent. Minute irregular surfaces 43 c areformed in the surfaces of concave parts 43 a and concave parts 43 b.

FIG. 18 is a perspective view schematically showing the structure of agrid convex part by cutting part of grid convex part 43, and correspondsto FIG. 9.

As shown in FIG. 18, grid convex part 43 is formed by making a pluralityof convex parts 43 a and a plurality of convex parts 43 b of virtually asemi-circular cross-sectional shape orthogonal to each other. By formingthe above convex parts in a grid pattern, it is possible to scatterlight incident on back surface 12 of light flux controlling member 40 ineither the vertical direction or the horizontal direction.

The cross-sectional shape of convex part 43 a has a similar shape to asemi-circle. For example, the length of the bottom surface of convexpart 43 a is 0.5 millimeters, the base angle is 45 degrees and R at thetip is 0.2 millimeters. A shape is possible where the inclining angle ofconvex part 43 a may be equal to or greater than 45 degrees or may besmaller than 45 degrees. The inclining angle of convex part 43 a ispreferably 45 degrees or greater for the purpose of appropriatelyscattering light incident on back surface 12 of light flux controllingmember 40.

Fine irregular surface 43 c is a rough surface of about 70 micrometersformed on the surface of convex part 43 a. Fine irregular surfaces 43 care created by performing etching processing to roughen the mold inwhich convex parts 43 a are formed.

As described above, with the present embodiment, by forming convex part43 in back surface 12 of light flux controlling member 40, it ispossible to appropriately scatter light incident on back surface 12 oflight flux controlling member 40, and, by forming the surfaces of convexparts 43 a and convex parts 43 b as fine irregular surface 43 c, it ispossible to improve scattering performance and further preventunevenness in illuminance.

Embodiment 3 Overall Shape of Light Flux Controlling Member

With above Embodiments 1 and 2, inventions for scattering light incidenton back surface 12 by providing grid convex part 13 (43) in back surface12 of light flux controlling member 4 (40) have been explained.

The present inventors have found that, by devising the shape of gridconvex part 13, it is possible to provide advantages of retroreflectinglight reflected by light diffusing member 2 and increasing the amount ofretroreflected light.

The invention as to the shape of grid convex part 13 for increasing theamount of retroreflected light will be explained with Embodiment 3.

FIGS. 19A and 19B are cross-sectional views of a light flux controllingmember of a light emitting apparatus according to the presentembodiment. FIG. 19A is an overall cross-sectional view of a light fluxcontrolling member, and FIG. 19B is a view enlarging part C shown inFIG. 19A. Note that, in FIGS. 19A and 19B, the same components as inFIGS. 7A and 7B will be assigned the same reference numerals andexplanation thereof will be omitted.

Light flux controlling member 50 is used instead of light fluxcontrolling member 4 of FIG. 4 and FIG. 11.

In comparison of light flux controlling member 50 shown in FIG. 19A withlight flux controlling member 4 shown in FIG. 7A, the shape of gridconvex part 53 differs from the shape of grid convex part 13.

Grid convex part 53 is transferred from the mold using transparent resinmaterial such as PMMA, PC and EP, to back surface 12 of light fluxcontrolling member 50, and is formed integrally with light fluxcontrolling member 50.

As shown in FIG. 19B, grid convex part 53 is formed by aligning aplurality of strips of convex parts 53 a projecting outward from backsurface 12 of light flux controlling member 50, such that the ridgelines of these convex parts 53 a become parallel, and by aligning aplurality of strips of convex parts 53 b orthogonal to those convexparts 53 a, such that the ridge lines of these convex parts 53 b becomeparallel. Then, square-pyramidal concave parts are formed between convexparts 53 a and convex parts 53 a that are adjacent and between convexparts 53 b and convex parts 53 b that are adjacent. The cross-sectionalshapes of convex part 53 a and convex part 53 b orthogonal to thedirection in which strips extend are isosceles triangles.

Here, grid convex part 53 only needs to be provided in a predeterminedarea from the center of back surface 12 of light flux controlling member50 to the outer periphery, and may be formed in the entire surface ofback surface 12 of light flux controlling member 50.

[Explanation of Convex Parts 53 a of Grid Convex Parts 53 andRetroreflected Light]

Part of light emitted from light control/emission surface 11 of lightflux controlling member 50 is reflected by light diffusing member 2without transmitting through light diffusing member 2 (see FIG. 5). Partof light reflected by light diffusing member 2 is incident on lightcontrol/emission surface 11.

As shown in FIGS. 19A and 19B, by forming convex parts 53 a of gridconvex part 53 as isosceles triangles, light incident on lightcontrol/emission surface 11 is retroreflected by convex parts 53 a andis emitted again from light control/emission surface 11.

FIGS. 20A and 20B and FIGS. 21A and 21B show how light which isreflected by light diffusing member 2 and is incident on lightcontrol/emission surface 11 is retroreflected by convex parts 53 a. FIG.20A shows the case where inclining angle θ which is an angle formedbetween the bottom surface (i.e. reference surface) and the pyramidsurface is 45 degrees, and FIG. 21A shows the case where inclining angleθ is 55 degrees. Further, FIG. 20B is a view enlarging part C shown inFIG. 20A, and FIG. 21B is a view enlarging part C shown in FIG. 21A.

As shown in FIGS. 20A and 20B, in case of θ=45 degrees, part of light 54incident from the direction vertical to the reference plane is reflectedtotally inside one convex part 53 a, and is emitted again from lightcontrol/emission surface 11.

By contrast with this, as shown in FIGS. 21A and 21B, in case of θ=55degrees, part of light 54 incident on light control/emission surface 11from the direction vertical to the reference plane reflects and refractsto pass between a plurality of convex parts 53 a, and is emitted againfrom light control/emission surface 11.

Light reflected totally inside one convex part 53 a is brighter thanlight emitted reflecting and refracting to pass between a plurality ofconvex parts 53 a. That is, the amount of retroreflected light is great.

Note that, in case of θ=45 degrees, light incident from directions otherthan the direction vertical to the reference plane includes lightemitted reflecting and refracting to pass between a plurality of convexparts 53 a. Accordingly, it is not necessarily appropriate to say thatthe amount of retroreflected light is the greatest in case of θ=45degrees.

[Simulation Result]

The present inventors conducted a simulation about the relationshipbetween inclining angle θ and the amount of retroreflected light toverity the advantage of the present embodiment. FIG. 22 shows thissimulation result.

The horizontal axis of FIG. 22 indicates inclining angle θ. Further, thevertical axis of FIG. 22 represents the rate of the amount of lightreaching surface 18 a (i.e. light receiving surface) of substrate 18 incase where the inclining angle is 0 degree (that is, the back surface 12has a planar surface).

That is, when the value on the vertical axis of FIG. 22 is smaller, theamount of retroreflected light is greater. As shown in FIG. 22, thesimulation found that the amount of retroreflected light maximized wheninclining angle θ was about 55 degrees.

[Variation]

Further, as shown in above FIG. 10, the amount of light incident on backsurface 12 is greater in a part closer to light emitting element 3.

As shown in FIG. 23, it is equally possible to apply treatment (e.g.engraving treatment) mainly for the purpose of scattering light, in area55 a predetermined distance apart from the center of back surface 12,and apply treatment (treatment for providing grid convex part 53) mainlyfor the purpose of retroreflection, in other area 56 of back surface 12.In this way, by forming a light scattering part in area 55 (i.e. innerarea) in which light from light emitting element 3 frequently enters andwhich is near the periphery of concavity 14 and by forming aretroreflecting part in area 56 (i.e. outer area) which is distant fromconcavity 14 on back surface 12 and which light from light emittingelement 3 hardly reaches, it is possible to effectively realize twofunctions of scattering and retroreflecting light.

As described above, with the present embodiment, by forming grid convexpart 53 formed with convex parts 53 a and convex parts 53 b havingisosceles-triangular cross-sectional shape, in back surface 12 of lightflux controlling member 50, it is possible to effectively utilize lightreflected by light diffusing member 2 by retroreflecting this light toilluminate light diffusing member 2 again, so that it is possible toreduce the amount of decrease in luminance on a display surface.

There are cases where reflective sheets are installed above surface 18 aof substrate 18 of the display apparatus in order to reduce the amountof decrease in luminance on the display screen. With the presentembodiment, light retroreflected by light flux controlling member 50transmits through light diffusing member 2 and is radiated on thedisplay screen (i.e. illuminated surface), so that it is possible toprevent unevenness in luminance on the display screen without placingreflective sheets under light emitting apparatuses 5 in substrate 18 andprovide high quality of illumination.

Embodiment 4

A case will be explained with Embodiment 4 where a grid pattern of aplurality of concave parts is formed in the back surface of a light fluxcontrolling member.

FIGS. 24A and 24B are cross-sectional views of a light flux controllingmember of a light emitting apparatus according to the presentembodiment. FIG. 24A is an overall cross-sectional view of a light fluxcontrolling member, and FIG. 24B is a view enlarging part C shown inFIG. 24A. Note that, in FIGS. 24A and 24B, the same components as inFIGS. 19A and 19B will be assigned the same reference numerals, andexplanation thereof will be omitted.

Light flux controlling member 60 is used instead of light fluxcontrolling member 50 of FIG. 19A to FIG. 23.

Light flux controlling member 60 shown in FIG. 24A differs from lightflux controlling member 50 shown in FIG. 19A in providing grid concavepart 63 instead of grid convex part 53. Concave parts 63 a and concaveparts 63 b are formed instead of convex parts 53 a and convex parts 53 bof light flux controlling member 50.

Grid concave part 63 is formed by aligning a plurality of recessedstrips of concave parts 63 a, such that the ridge lines of these concaveparts 63 a become parallel, and by aligning a plurality of recessedstrips of concave parts 63 b orthogonal to those concave parts 63 a,such that the ridge lines of these concave parts 63 b become parallel.Then, square-pyramidal convex parts 63 c are formed between concaveparts 63 a and concave parts 63 a that are adjacent and between convexparts 63 b and convex parts 63 b that are adjacent.

A plurality of square-pyramids of convex parts 63 c projecting outwardfrom back surface 12 of light flux controlling member 60 are transferredfrom the mold using transparent resin material such as PMMA, PC and EP,and are formed integrally with light flux controlling member 60.

Note that grid concave part 63 only needs to be provided in apredetermined area from the center of back surface 12 of light fluxcontrolling member 60 to the outer peripheral surface, or may be formedin the entire surface of back surface 12 of light flux controllingmember 60.

The present embodiment can also scatter light incident from lightemitting elements, on the back surface of the light controlling member.

Embodiment 5

Although cases have been explained with the above embodiments where asquare grid pattern of a plurality of concave parts or a plurality ofconvex parts is formed in the back surface of the light flux controllingmember, the present invention is not limited to this, and a triangulargrid pattern or a hexagonal grid pattern of a plurality of concave partsor a plurality of convex parts may be formed.

Cases will be explained with Embodiment 5 where a triangular gridpattern or a hexagonal grid pattern of a plurality of concave parts or aplurality of convex parts is formed in the back surface of a light fluxcontrolling member.

[Variation 1]

Variation 1 according to the present embodiment provides a case where atriangular grid pattern of a plurality of convex parts is formed in theback surface of a light flux controlling member. FIGS. 25A, 25B and 25Cschematically show the structure of grid concave parts by cutting partof the back surface of the light flux controlling member of variation 1of a light emitting apparatus according to the present embodiment. FIG.25A is a perspective view, FIG. 25B is a bottom view and FIG. 25C is aside view.

As shown in FIGS. 25A, 25B and 25C, grid convex part 73 is formed byaligning a plurality of strips of convex parts 73 a projecting outwardfrom the back surface of the light flux controlling member, aligning aplurality of convex parts 73 b such that 60 degrees are formed betweenconvex parts 73 b and convex parts 73 a, and aligning convex parts 73 csuch that 60 degrees are formed between convex parts 73 c, convex parts73 a and convex parts 73 b. Moreover, triangular-pyramidal concave partsare formed in parts surrounded by convex parts 73 a, convex parts 73 band convex parts 73 c. The cross-sectional shapes of convex part 73 a,convex part 73 b and convex part 73 c orthogonal to the direction inwhich strips extend are isosceles triangles.

[Variation 2]

Variation 2 according to the present embodiment provides a case where atriangular grid pattern of a plurality of concave parts is formed in theback surface of the light flux controlling member. FIGS. 26A, 26B and26C schematically show the structure of grid concave parts by cuttingpart of the back surface of a light flux controlling member of variation2 of the light emitting apparatus according to the present embodiment.FIG. 26A is a perspective view, FIG. 26B is a bottom view and FIG. 26Cis a side view.

As shown in FIGS. 26A, 26B and 26C, grid concave part 83 is formed witha plurality of triangular pyramids of convex parts 83 d projectingoutward from the back surface of the light flux controlling member. In atriangular grid in which a plurality of concave parts 83 a, a pluralityof concave parts 83 b and a plurality of concave parts 83 are formed tocross at 60 degrees, these triangular-pyramidal concave parts 83 d areformed in parts surrounded by concave parts 83 a, concave parts 83 b andconcave parts 83 c.

[Variation 3]

Variation 3 according to the present embodiment provides a case where ahexagonal grid pattern of a plurality of convex parts is formed in theback surface of a light flux controlling member. FIG. 27 is a bottomview schematically showing the structure of grid concave parts bycutting part of the back surface of the light flux controlling member ofvariation 3 of the light emitting apparatus according to the presentembodiment.

As shown in FIG. 27, grid concave part 93 is formed by arranging ahexagonal grid pattern of ridge lines of a hexagon (i.e. bold concavepart 93 a indicated in FIG. 27), in the back surface of the light fluxcontrolling member. Moreover, hexagonal-pyramidal concave partssurrounded by hexagonal concave parts 93 a are formed.

[Variation 4]

Variation 4 according to the present embodiment provides a case where ahexagonal grid pattern of a plurality of concave parts is formed in theback surface of a light flux controlling member. In the light fluxcontrolling member according to variation 4, a hexagonal groove (i.e.bold concave part 103 a of FIG. 27) is formed instead of hexagonalconvex part 93 a according to above-described variation 3.

Grid concave parts 103 a are formed by arranging a hexagonal gridpattern of hexagonal grooves (i.e. concave parts) 103 a, in the backsurface of a light flux controlling member. Then, hexagonal-pyramidalconcave parts surrounded by hexagonal concave parts 103 a are formed.

With each variation according to the present embodiment, it is possibleto scatter light incident on the back surface of a light controllingmember from light emitting elements.

Note that, as in Embodiment 1, Embodiment 2, Embodiment 3 and variation1 according to Embodiment 5, processing a mold is easy when strips areformed in a product (i.e. light flux controlling member).

The above explanation is an illustration of preferable embodiments ofthe present invention, and the scope of the present invention is notlimited to these.

For example, a light diffusing member may be attached to the surface onthe light emitting element side of a member-to-be-illuminated, or may bearranged on the side of the surface facing the light emitting element ofthe member-to-be-illuminated in a state where the light diffusing memberis provided separately from the member-to-be-illuminated.

Further, the light flux controlling member may form an engraved surfacein a light control/emission surface to diffuse light emitted from thelight control/emission surface.

Furthermore, the light flux controlling member may be made of materialincluding light diffusion material (for example, silicon particles andoxidized titanium).

Still further, although the names “light emitting apparatus,” “surfacelight source apparatus,” and “display apparatus” have been used with theabove embodiments for ease of explanation, names such as “planar lightsource” and “display element” are equally possible.

INDUSTRIAL APPLICABILITY

The light emitting apparatus, surface light source apparatus and displayapparatus according to the present invention can be widely used forvarious illuminations in, for example, television monitors, backlightsof monitors of personal computers and interior lights.

REFERENCE SIGNS LIST

-   1 SURFACE LIGHT SOURCE APPARATUS-   2 LIGHT DIFFUSING MEMBER-   3 LIGHT EMITTING ELEMENT-   4, 40, 50 LIGHT FLUX CONTROLLING MEMBER-   5 LIGHT EMITTING APPARATUS-   6 DISPLAY APPARATUS-   7 MEMBER-TO-BE-ILLUMINATED-   11 LIGHT CONTROL/EMISSION SURFACE-   12 BACK SURFACE-   13, 43, 53, 73, 93 GRID CONCAVE PART-   13 a, 13 b, 43 a, 43 b, 53 a, 53 b, 73 a, 73 b, 93 a CONVEX PART-   14 CONCAVITY-   15 FLANGE-   16 LEG-   18 SUBSTRATE-   43 c IRREGULAR SURFACE-   63, 83, 103 GRID CONCAVE PART-   63 a, 83 a, 83 b, 83 c, 103 a CONCAVE PART-   93 a RIDGE LINE

What is claimed is:
 1. A surface light source apparatus comprising: alight emitting element that emits light; a light flux controlling memberthat controls light emitted from a light emitting element; and a lightdiffusing member that scatters light and allows transmission of lightemitted from the light emitting apparatus, wherein the light fluxcontrolling member comprises: a light control/emission surface thatcontrols a traveling direction of the light emitted from the lightemitting element; a concavity that allows a main beam to be incidentinside, the main beam being light emitted in a predetermined range of anangle from a reference optical axis serving as a center axis ofthree-dimensional light fluxes emitted from the light emitting element;and a back surface that extends in a radial direction from an openingrim part of the concavity and that allows sub-beams to be incidentinside, the sub-beams being light other than the main beam emitted fromthe light emitting element, wherein one of a grid convex part whicharranges a plurality of strips of convex parts in a grid pattern and agrid concave part which arranges a plurality of strips of concave partsin a grid pattern, is formed in the back surface of the light fluxcontrolling member, and wherein surface roughening treatment is appliedto one of the strips of the convex parts and the strips of the concaveparts.
 2. The surface light source apparatus according to claim 1,wherein the grid pattern is a square grid.
 3. The surface light sourceapparatus according to claim 1, wherein the grid pattern is a triangulargrid.
 4. The surface light source apparatus according to claim 1,wherein the grid pattern is a hexagonal grid.
 5. The surface lightsource apparatus according to claim 1, wherein one of the grid convexpart and the grid concave part is integrally molded with the backsurface of the light flux controlling member.
 6. The surface lightsource apparatus according to claim 1, wherein one of the strips of theconvex parts and the strips of the concave parts each comprise across-sectional shape that is orthogonal to a direction in which thestrips extend and that comprises one of a triangular shape, a triangularshape having a vertex subjected to R-chamfer processing, and asemi-circular shape.
 7. The surface light source apparatus according toclaim 1, wherein, when the grid convex part is formed in the backsurface, a groove part between the strips of the convex parts comprisesa round shape.
 8. The surface light source apparatus according to claim1, wherein, when the grid convex part is formed in the back surface, thestrips of the convex parts comprise a triangular cross-sectional shapethat is orthogonal to a direction in which the strips of the convexparts project, and an inclining angle of 55 degrees that is an angleformed between a bottom side and another side.
 9. The light fluxcontrolling member according to claim 1, wherein the one of the gridconvex part and the grid concave part, which is formed in the backsurface, scatters the sub-beams.
 10. The light flux controlling memberaccording to claim 1, wherein the light control/emission surfaceincludes: a first emission surface that is positioned in a predeterminedrange around the reference optical axis and that has a shape of a smoothcurved surface dented downward; a second emission surface that is formedto continue to the periphery of the first emission surface and that hasa smooth curved shape bulging upward; and a third emission surface thatis formed to continue to the periphery of the second emission surface.11. The light flux controlling member according to claim 1, whereinengraving treatment is applied to an area of the back surface that is apredetermined distance apart from the center of the back surface.